The invention relates to a method for producing a recessed steel piston ring that is provided with a wear-resistant layer.
DE 102 21 800 A1 discloses a method for generating wear protection layers on a steel piston ring by providing at least a portion of the running surface with a running surface coating in a first work step, and providing at least the flanks with a nitride layer by way of plasma nitriding in a second work step, so as to generate a hardness HV 0.1<1400, so that the work step of plasma nitriding is carried out depending on the running surface coating that is used in a temperature range of <490° C.
A steel piston ring is known from DE 10 2005 023 627 A1, comprising a running surface having a recess on one side, upper and lower flanks, and an inner circumferential surface, wherein the running surface is coated with a chromium ceramic-based wear protection layer having microcracks, and at least the flanks are provided with a wear-reducing nitride layer, so that at least one of the regions where the flank transitions into the running surface has an approximately sharp-edged design.
When a recessed PVD-coated steel piston ring is implemented, a sharp functional edge is required. Because of the need for surface nitriding, this was previously not an option. A nitrided edge requires an edge radius of no more than 0.1 mm.
A person skilled in the art considers a sharp edge produced in a standard manner to have rounded region of max. R<0.05 mm.